System of generator regulation



NOV. 9, 1948. w J RADY 2,453,341

SYSTEM OF GENERATOR REGULATION Filed Sept. 26, 1944- L llll n 'VENTOR BY 7624A ATTORNEW Patented Nov. 9, 1948 2,453,341 SYSTEM OF GENERATOR REGULATION William J. Rady, Anderson, eral Motors Corporation,

poration of Delaware Ind., assignor to Gen- Detroit, Mich, a cor- Application September 26, 1944, Serial No. 555,882

6 Claims. 1

This invention relates to carbon-pile voltage regulation for a variable speed generator. As the speed of the generator varies, there is considerable variation in the field current controlling resistance of the carbon-pile required to control highfield current at low speed and low field current at high speed. Since there is a limit to which the carbon-pile resistance can be varied by an electromagnet responsive to generator voltage, the use of a carbon-pile regulator has been limited.

An object of the present invention is to make possible the use of a carbon-pile regulator to control the voltage of a generator whose speed varies between very wide limits. This object is accomplished by the provision of a variable resistance by-pass around generator field and means for controlling the by-pass in a manner such that, at low speed when the field current is high, the by-pass will have high resistance, and that, at high speed when the field current is low, the bypass will have relatively low resistance. The result is that, throughout a wide range of generator speed, the variation in current flowing through the carbon-pile of the voltage regulator is much less than the variation in the current flowing through the generator field.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawing, wherein a preferred form of embodiment of the present invention is clearly shown.

The figure of the drawing is a wiring diagram showing an embodiment of the invention.

Referring to the drawing, a generator is connected by a relay H with a storage battery 22. When the generator 20 obtains a voltage sufficient to charge the battery, relay 2| closes; and relay 2| opens when generator voltage falls a predetermined amount below battery voltage. The generator 20 has a shunt field winding 23 in series with the carbon-pile 3! of a regulator 30 which comprises a coil 32 responsive to generator voltage and surrounding a core 33 cooperat-' ing with an armature 34 attached to a rod 35 with which a laminated leaf spring 36 is connected. Spring 35 is normally biased upwardly so as to exert a predetermined pressure upon the discs of the carbon-pile 3|, Spring 36 so cooperates with abutments 36a that the force of the spring 36 increases in proportion to the increase of magnetic pull as the air gap between the armature 34 and the core 33 decreases.

The instrument 40 includes a carbon-pile 4i shunting the field winding 23. As the pile ll provides a by-pass around the field winding 23, the instrument 40 may be called a by-pass controller. The controller Ml has a coil 42 responsive to generator voltage surrounding a core Q3 cooperating with an armature M attached to a rod 15 which extends from the armature M upwardly through the fixed terminal t la of the pile and the washer like discs of the pile 4i and which is attached to the movable terminal Mb. A spring :6 is attached to the rod 45 and bears against abutments 45a. The force of the spring it increases in proportion to the magnetic pull as the gap between the armature M and the core 53 decreases.

Spring 46 normally locates the terminal lb against a stop die. The pile M is normally practically open-circuited. Core S3 is surrounded by a magnet coil 2? responsive to voltage impressed upon field winding 23. The coils 12 and 47 are in bucking relation as indicated by arrows Ma and did.

At low speed when the relay 2i closes, the field current is relatively high. The magnetic effects of coils 42 and All are then substantially equal so that the spring 36 holds the upper terminal ilb against the stop t le. The by-pass pile M is practically open circuited. A small change in resistance of pile 3! will control the voltage drop across the field winding 23 and the coil 41. This voltage drop is at the maximum controlled valueat low speed. As the generator speed increases. this voltage drop should decrease because field strength should decrease in order to limit the generator voltage. This voltage drop is generator voltage less the voltage drop in the pile 3 i. If the current in pile 3! were no greater than the field current, it is apparent that pile 3i must have very high resistance at nigh speed,

The present system of regulation provides for so decreasing the resistance of by-pass 4! as speed increases that the current which passes through pile 31 decreases at a rate which is much less than the rate of decrease of field current. Therefore the resistance of pile 3| will be much less at maximum speed than would be the case if pile 3| carried only the field current.

The decrease of resistance of by-pass pile M with increasing speed is eiiected in the following manner. As re ulator operates to increase the resistance of pile 3| with speed increase, the voltage drop across coil H of controller All decreases, and coil 42 becomes increasingly effective to oppose spring 46 and to cause upper terminal Mb to be increasingly forced toward terminal Ma to increase the compression of pile 6i. As its re sistance decreases, the amount of current in pile 4! increases. With increasing speed, current in pile 4i increases although current in field winding 23 decreases. rent in pile 3i decreases at a rate substantially less than the rate of decrease of field current. Therefore the regulator 30 is able to control the voltage drop across field winding 23 over a wide range of generator speeds because the amount of resistance in pile 3i required for regulation is much less than it would have been if pile 3i carried only the current in field winding 23.

In order that the controller ill will not be affected by sudden changes in field current, the field 23 is connected with the primary 5d of a transformer whose secondary iii is connected with a coil 52 surrounding the core 43. When there is a sudden reduction of field current resulting from a sudden reduction of voltage drop across field 23 and across coil ll, coil 52 aids coil 47. When there is a sudden increase of current in field winding 23 due to a sudden increase in voltage drop across field Winding 23 and across coil 41, coil 52 opposes coil 4177. In this way stability of the controller 48 is maintained.

While the embodiment of the present invention as herein disclosed, constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. A system of regulation for a variable speed generator having an armature and comprising a generator shunt field winding and a variable resistance unit connected in parallel, one end of the parallel circuit being connected with one terminal of the armature, a carbon pile connected with the other terminal of the armature and with the other end of the parallel circuit, a spring normally biasing the carbon pile into low resistance status, an electromagnet opposing said spring and having a magnet coil responsive to generator voltage and tending to increase the resistance of' the carbon pile as generator voltage tends to increase whereby, as speed increases, the voltage drop across the-carbon pile increases and the voltage drop across the ends of the parallel circuit tends to decrease, and means responsive to the decrease in voltage drop across the ends of the parallel circuit for causing decrease in the resistance 0f the variable resistance unit whereby, as speed increases, current in the variable resistance increases and current in the shunt field winding decreases.

2. A system of regulation for a variable speed generator having a shunt field winding comprising a carbon-pile regulator having a carbon-pile for controlling the voltage impressed upon the generator field winding and means responsive to generator voltage for varying the resistance of the carbon-pile, a variable resistance lby-passing the generator field Winding, and means responsive to decrease of voltage impressed on the gen- Consequently the total cur- 4 erator field winding for decreasing the by-pass resistance, said means including an electromagnet having bucking coils, one of which is responsive to generator voltage and the other to voltage impressed on the generator field winding.

3. A system of regulation for a variable speed generator having a shunt field winding comprising a carbon pile regulator having a carbon-pile for controlling the voltage impressed upon the generator field winding and means responsive to generator voltage for varying the resistance of the carbon-pile, a second carbon-pile lay-passing the generator field winding, 8. spring tending to increase the resistance of the second carbonpile, and an electromagnet opposing the spring for decreasing the resistance of the second carhon-pile and having bucking coils, one of which is responsive to generator voltage and the other to voltage impressed on the generator field windmg.

4. A system of regulation for a variable speed generator having an armature and comprising a generator shunt field winding and a variable resistance unit connected in parallel, one end of the parallel circuit being connected with one terminal of the armature, a carbon pile connected with the other terminal of the armature and with the other end of the parallel circuit, a spring normally biasing the carbon pile into low resistance status, an electromagnet opposing said spring and having a magnet coil responsive to generator voltage and tending to increase the resistance of the carbon pile as generatorvoltage tends to increase whereby, as speed increases, the voltage drop across the carbon pile increases and the voltage drop across the ends of the parallel circuit tends to decrease, means responsive to the decrease in voltage drop across the ends of the parallel ircuit for causing decrease in the resistance of the variable resistance unit whereby, as speed increases, current in the variable resistance increases and current in the shunt field winding decreases and provisions for nullifying the effect on said means due to voltage induced in the generator field winding by virtue of sudden change in current therein.

5. A system of regulation for a variable speed generator having a shunt field winding comprising a carbon-pile regulator having a carbon-pile for controlling the voltage impressed upon the generator field winding and means responsive to generator voltage for varying the resistance of the carbon-pile, a variable resistance by-passing the generator field winding, and means responsive to decrease of voltage impressed on the generator field winding for decreasing the by-pass resisttance, said means including an electromagnet having bucking coils, one of which is responsive to generator voltage and the other to voltage impressed on the generator field winding and having another magnet coil which is inductively related to the generator field and which is so wound that it aids the coil responsive to voltage impressed on the generator when there is a sudden decrease of field current, and bucks it when there is a sudden increase of field current.

6. A system of regulation for a variable speed generator having a shunt field winding comprising a canbon-pile regulator having a carbon-pile for controlling the voltage impressed upon the generator field winding and means responsive to generator voltage for varying the resistance of the carbon-pile, a second carbon-pile by-passing the generator field winding, 2. leaf spring tending to increase the resistance of the second caribou- 5 6 pile, and an electromagnet opposing the spring that it bucks the second windingwhen there is a for decreasing the resistance of the second carsudden increase of field current. \bon-pile and including an armature, core and WILLIAM J. RADY. windings, an abutment member engaged "by the end of the spring and so related thereto that in- 5 REFERENCES CKTEEB' crease in spring force is substantially pr p The following references are of record in the tionate to increase in magnetic force opposing the me of this patent; spring as the gap between the armature and core decreases, said windings being three in number: UNITED STAFES PATENTS (1) a winding responsive to generator voltage (2) 10 N b N D t a winding responsive to voltage impressed 0n t e 1,252,511 Turbayne -s Jan. 8, 1918 generator field winding (3) a winding inductively 1,733,142 Sayres at ,1 Nov 25, 1930 related to the generator field winding and 50 1,933,858 Keller Nov. 7, 1933 wound that it aids the second Winding when there is a sudden decrease of field current and 15 

